Various electronic devices are mounted on a vehicle. In order to perform power supply and signal transmission to the various electronic devices, an electric junction box is disposed at an appropriate position of the vehicle. The electric junction box uses a waterproof box so as to prevent water from penetrating thereinto during traveling under a rainy weather or during vehicle washing. The waterproof box has various structures, but generally includes, for example, a body case that accommodates a plurality of electrical components, and a cover that covers an opening of the body case (e.g., refer to Patent Literature 1). Also, FIG. 8 illustrates a plan view of a body case of a waterproof box used in an electric junction box according to the related art.
A body case 303 illustrated in FIG. 8 is made of a synthetic resin and includes a frame-shaped peripheral wall 339. An opening of the body case 303 is covered by a cover (not illustrated) made of a synthetic resin. Also, the peripheral wall 339 has a double-wall structure including an outer wall 331 and an inner wall 332. Water entering from a seam between the cover and the outer wall 331 passes between the outer wall 331 and the inner wall 332 and is discharged to the outside of the body case 303. That is, the waterproof box including the body case 303 and the cover as described above prevents water from splashing on the electrical components by configuring the peripheral wall 339 with the double-wall structure, without using packing.